In general, inkjet printers include at least one printhead configured with an array of inkjet ejectors that are operated to eject drops of liquid ink onto an image receiving surface. A phase-change inkjet printer employs phase change inks that are solid at ambient temperature, but transition to a liquid phase at an elevated temperature. The melted ink can then be ejected by the inkjet ejectors in a printhead to form an ink image on the image receiving surface. The image receiving surface may be an intermediate imaging member, such as a rotating drum or belt, on which a layer of release agent has been applied. After the ink image is formed on the release agent layer, the image is then transferred to an image receiving substrate, such as a sheet of paper, as the substrate passes through a nip formed between a transfix roller and the intermediate imaging member. In other printing systems, the ink can be ejected directly onto printing media as the media moves past the printheads.
As already noted above, phase change ink is loaded into a printer in solid form, transported to a melting device, and melted to produce liquid ink. The melted ink can be stored in a reservoir that can be either internal or external to a printhead. Some printers include both internal and external reservoirs, with the reservoir internal to the printhead(s) refilling from the external reservoir when the ink in the internal reservoir is low.
In phase change inkjet printers having multiple printheads, the ink is used at varying rates by each printhead. These varying rates of use necessitate independent refilling of the internal ink reservoir of each printhead. Previous printers used a series of ball valves, flapper valves, solenoids, pressure sources, and other mechanical hardware to enable individual refilling of each internal reservoir from the external reservoir. However, the mechanical ink transport systems can be slow at responding to changes in ink levels in the internal reservoirs, and the mechanical transport systems have a large number of parts that can malfunction. Thus, improved transport of liquid ink in a phase change ink printer is desirable.